My breastshot waterwheel design and questions

[Dave Turpin]

Hello all!

I just moved back to Seattle and was hoping that when I finally bought my first house I would install alternate power sources. I was hoping for wind power but lo and behold it just isn't windy here. Nor is solar a great idea. Lucky for me, on the fifth day of house hunting a new house came on the market that not only is beautiful and fills my needs, but it also has a healthy creek running right through the front yard.

So I have this to work with:

http://i207.photobucket.com/albums/bb21/bpestilence/DSCN1241.jpg

http://i207.photobucket.com/albums/bb21/bpestilence/DSCN1242.jpg

I am going to need to tear out that bridge anyway (mine is the wood and asphalt one), so I came up with this waterwheel design:

http://i207.photobucket.com/albums/bb21/bpestilence/hydro2.jpg

http://i207.photobucket.com/albums/bb21/bpestilence/hydro1.jpg

The design is a 6' tall wheel, 3' wide, with a 2' weir and flowing at least 9 cfs. I calculated the actual flow right now as 15 cfs. It may slow to a trickle in the summer, but Seattle is pretty fair with the rain at most times.

I further calculated that at 9 cfs, the wheel will rotate at 21 RPM and can theoretically produce 1.75 BHP or 1300 W at the design 9 cfs flow rate.

Now. My questions are how to get the power to the house. Right now I am planning to use the WindBlue DC-540 PMA with a 20:1 helical gear reducer installed as a step-up gearbox. This would give me 400 RPM at the alternator, which according to windblue should produce 36 VDC. Now the problem comes if the water pressure doubles, which it easily will after a rain. Double the flow rate and I get about 700 RPM which gives me 65 VDC. (I plan to run 10AWG 3-strand wire from the PMA pigtail to a rectifier in the house near the inverter)

Now assume that I build it strong enough to handle whatever I throw at it. Depending on the flow rate, I can see anything from 12-100 VDC at the rectifier, at up to 2 kW of power. Where can I get a grid tie inverter that can handle such a large input voltage range? Everything I see seems to be designed for solar power and is either 12-24 VDC, 24-48 VDC or 36-72 VDC. If the voltage gets too high I will fry these type of inverters.

I also designed in a 13" cable disc brake to stop the wheel for maintenance.

[Ben Colla]

How far do you have to run the cables?
Personally I'd aim at a higher voltage, espcially if you are aiming at grid connect, rather than dumping it into batteries. It's just cheaper if you run say 350v into your inverter than 24 or 48.

The power one aurora accepts voltages from about 90v to 600.

Idea :
How long is the creek on your property. Could you build a small weir at the high end, run 6" PVC pipe from there to the other end, keeping it level and then have say a 10' drop. This should then lead straight into a water turbine of some sort. That way you have constant pressure, excess just runs away and you probably end up with more power anyway.

I'm thinking something like http://www.exmork.com/medium-water-head-turbine.htm
*** Note I have no idea what that is like, it could be crap, but I am planning to buy one of their wind turbines at some point)

As it is, all you get is the power of the water running past the turbine.

[Dave Turpin]

The unrectified power from the PMA would go about 100 feet. I could go with a larger ratio gearbox and step the alternator speed up, I suppose. I couldn't over-volt the inverter you mentioned even at the design 3000 RPM limit of the PMA, but the DC-540 doesn't produce 90 VDC until 1000 RPM, which would require a pretty steep 50:1 gearbox.

[Rob Beckers]

Maybe look for a different PMA...
That voltage is very low, and consequently your losses will be very large, even at 100'. The Aurora wind inverters accept from 50V DC and up, which means only 38V 3-phase AC. Still, you're looking at either very thick wiring or large losses at such low voltages.

-RoB-

[Dave Turpin]

Thank for the advice!

After further searching I found a reversible 100:1 reducer. That would definately make the DC-540 blow up. But the DC-512 (which is supposedly designed for motor applications) would do fine from a trickle in the stream to nearly a flood, from 45-145 volts. I think I can find an inverter that can survive in that range.

The faster geartrain speed will make it less mechanically efficient, but the higher voltage should reduce transmission losses... So maybe it will equal out.

Do you see anything wrong with the basic design?

[Rob Beckers]

Hi Dave,

First, you're lucky to have such a resource! Water is one of the better ways to make energy. Even if just 1kW, it adds up when running 24x7! Seattle should be pretty good in keeping it flowing. No shortage of rain there.

I'm not sure why you would want to use a 50:1 or even 100:1 gearbox. Those are pretty steep ratios: The slightest bit of resistance or cogging on the alternator side and it'll never get started. How about using another PMA, for example Ginlong's high-voltage 1800 Watt (http://www.ginlong.com/wind-turbine-pmg-pma-permanent-magnet-generator-alternator-GL-PMG-1800.htm) one? The stock one is not great, the voltage is too high for the Aurora inverter, but they'll wire one up in delta instead of wye if you ask them for it (at a small additional price). That will cut the voltage by a factor of 1.7 from stock.

You mention around 21 RPM and roughly a kW. Running a delta-wired Ginlong at 400 RPM (20:1 gearbox) will allow you to tap 1.4kW (if you have it, less will work too of course). You can run this up to 600 RPM and load it up to almost 3kW. The voltage would range from 200V phase-to-phase to 290 Volt. After rectifying you would just be hitting the sweet spot for a 3kW Power-One Aurora grid-tie inverter (they go up to 600V DC). You can program the Aurora to load up a specific amount for XX Volt, and increase as voltage increases, up to adding extra load (beyond what the water would dictate) at the top end so the RPM would be kept under control.

-RoB-

[Dave Turpin]

Hmmm. Where could I purchase one of these? Looks like I would have to order it from China. (Not that I am unfamiliar with that, I buy all my carbon fiber from China)

How much do these guys cost?

[Dave Turpin]

For S&G I mocked up the appropriate powertrain that you mention. A 20:1 gearbox and a Ginlong PMA:

http://i207.photobucket.com/albums/bb21/bpestilence/waterwheel_3.jpg

[Rob Beckers]

What drawing program do you use Dave? Is that SketchUp?

-RoB-

P.S. When you find out what those Ginlong PMAs cost please post. It's been a while since I saw any pricing on those.

[Dave Turpin]

It's SolidWorks. Works pretty well for simulations. It can render things and make them look real, too, if I had a better video card. But I don't.

edit:

I finally got an email back from ginlong. They are confused why I asked about Delta-wiring the leads. But hopefully they will get back again.

However, I did learn that the Ginlong GCI-2k inverter now has a UL 1741 certification. Specs are here:

http://www.ginlong.com/grid-tie-connected-inverters.htm

This inverter has the highest input voltage range that I have seen so far. 750 volts! Unfortunately that is only true for the little 2kw inverter and the big 10kw inverter. The others are not as good as the Aurora units. But For $950 (that's what I am told the price of the 2kw inverter is) I might go for it.

Edit 2: The Ginlong PMA is $690! Is that worth it? Maybe, but I am still surprised.

So now it looks like the price of this project will be about:
$690 for PMA
$950 for Inverter
$100 shipping
$300 scrap steel for waterwheel
$70 for 2" pillow block bearings
$100 for 20:1 reducer (on eBay, shipped)
$500 for 5 yards of concrete
$200 for materials to cast concrete
$300 worth of cinder block
$300 for wiring
$200 for permits
$100 for inspection
==============
$3800 for a waterwheel installation, if I do all the work myself.

Assuming that my power bill is $150 a month.... It would pay for itself in 2 years. But... More research is needed once I get "on site".

[Dave Turpin]

Well, back to the drawing board. The bank didn't accept our generous offer.

[Rob Beckers]

Dave, sorry to hear about the bank problems. I suppose they take a dim view of hydro turbines. Maybe better to present it as a "home improvement" case. People do get loans for that all the time (if they can put their home as equity behind it).

That $690 for the alternator is actually not a bad price. Good permanent magnet alternators are very expensive (Ginlong is on the low end of the price scale compared to the competition).

The inverter is incredibly cheap! I certainly can't compete with that (even wholesale I pay just about twice as much). Their alternators have a good reputation, hopefully that extends to their inverters as well.

I suppose that delta wiring of the alternator is not so important if the inverter goes up to 750V. On the other hand, if you ever want to hook this up to a 600V inverter it becomes critical, so maybe you should insist. They shouldn't be confused; others have received delta wired alternators from them.

-RoB-

[Dave Turpin]

No, I mean we didn't get the house. This is the second house on te street we have bid on that has been rejected. And I offered 6% more than asking price!

This market sucks. Nobody is buying houses and because of that nobody is selling houses. I think some real estate developer bought it cash. They'll probably tear down the house and put 15 apartments on it.

edit:

Not all is lost. I might not be able to make a waterwheel but I am putting in an offer on a house that has excellent solar potential. I am going to go green dammit!